Structure and properties of collagen vitrigel membranes for ocular repair and regeneration applications

The frequency of ocular injuries on the battlefield has been steadily increasing during recent conflicts. Combat-related eye injuries are difficult to treat and solutions requiring donor tissue are not ideal and are often not readily available. Collagen vitrigels have previously been developed for corneal reconstruction, but increased transparency and mechanical strength are desired for improved vision and ease of handling. In this study, by systematically varying vitrification temperature, relative humidity and time, the collagen vitrigel synthesis conditions were optimized to yield the best combination of high transparency and high mechanical strength. Optical, mechanical, and thermal properties were characterized for each set of conditions to evaluate the effects of the vitrification parameters on material properties. Changes in denaturing temperature and collagen fibril morphology were evaluated to correlate properties with structure. Collagen vitrigels with transmittance up to 90%, tensile strength up to 12 MPa, and denaturing temperatures that significantly exceed the eye/body temperature have been synthesized at 40 °C and 40% relative humidity for one week. This optimal set of conditions enabled improvements of 100% in tensile strength and 11% in transmittance, compared to the previously developed collagen vitrigels.